The ethical dimension of personal health monitoring in the armed forces: a scoping review

Background Personal Health Monitoring (PHM) has the potential to enhance soldier health outcomes. To promote morally responsible development, implementation, and use of PHM in the armed forces, it is important to be aware of the inherent ethical dimension of PHM. In order to improve the understanding of the ethical dimension, a scoping review of the existing academic literature on the ethical dimension of PHM was conducted. Methods Four bibliographical databases (Ovid/Medline, Embase.com, Clarivate Analytics/Web of Science Core Collection, and Elsevier/SCOPUS) were searched for relevant literature from their inception to June 1, 2023. Studies were included if they sufficiently addressed the ethical dimension of PHM and were related to or claimed relevance for the military. After selection and extraction, the data was analysed using a qualitative thematic approach. Results A total of 9,071 references were screened. After eligibility screening, 19 articles were included for this review. The review identifies and describes three categories reflecting the ethical dimension of PHM in the military: (1) utilitarian considerations, (2) value-based considerations, and (3) regulatory responsibilities. The four main values that have been identified as being of concern are those of privacy, security, trust, and autonomy. Conclusions This review demonstrates that PHM in the armed forces is primarily approached from a utilitarian perspective, with a focus on its benefits, without explicit critical deliberation on PHM’s potential moral downsides. Also, the review highlights a significant research gap with a specific lack of empirical studies focussing specifically on the ethical dimension of PHM. Awareness of the inherent ethical dimension of PHM in the military, including value conflicts and how to balance them, can help to contribute to a morally responsible development, implementation, and use of PHM in the armed forces. Supplementary Information The online version contains supplementary material available at 10.1186/s12910-024-01086-0.

global mobile health market is expected to grow by 10.8% annually, reaching an estimated USD 130.6 billion in 2030, thus providing an expanding market of PHM technologies for armed forces to draw on [7].Therefore, PHM is an increasingly attractive technology for the armed forces.PHM can be defined as any electronic device or system carried by an individual, that longitudinally monitors and records data about a health-related aspect of that individual's life [8].
PHM is a form of wearable health technology that encompasses a range of devices, ranging from medicalgrade, specialised devices such as portable ECG monitors to consumer wearables like Apple or Garmin smartwatches.PHM has a variety of applications in the field of healthcare.These include prevention (e.g.promoting physical activity with a smartwatch to reduce cardiovascular disease [9]), diagnosis (e.g.detection of obstructive sleep apnoea [10]), treatment (e.g.continuous blood glucose monitoring in diabetes), support (e.g.surveillance of Influenza-like illness through Fitbit data [11]) and rehabilitation (e.g.gait support for patients with Parkinson's disease [12]).Furthermore, it is increasingly used by individuals to monitor and assist physical activities such as running or cycling.Additionally, PHM is emerging in the domain of occupational health management, for example to detect occupational physical fatigue [13].
Multiple studies have illustrated the potential benefits of PHM for specific problems in the military.For example, heat illness -for which soldiers are particularly at risk -causes substantial morbidity and can even be fatal [14].Such exertional heat illness can be monitored or prevented by remotely measuring specific biometric parameters [15].In addition, lack of sleep is a common stressor in the military operational environment.Fatigue and sleep deprivation are known to have a profoundly negative effect on human performance, thereby affecting military readiness [16].To improve the sleep of soldiers recently returned from deployment -a population at risk for significant sleep problems -it can be helpful to assess their sleep with a wrist activity monitor [17].Furthermore, remote physiological monitoring with a oximetry probe can assist in assessing the wearer's level of exertion, even in austere environments [18].This information can be helpful in preventing casualties and directing medical aid.
Existing literature on PHM in the military focuses on topics such as acceptability, reliability, technical feasibility, and accuracy.For example, it is shown by gathering user experience perspectives that body-worn PHM devices are well-accepted by soldiers, but that there is a preference for devices not worn around the chest or wrist [19].In addition, it has been demonstrated that a novel type of photoplethysmography (PPG) sensor device, which utilizes infrared light to detect blood volume changes in the peripheral circulation, provides more accurate and reliable biodata in high-motion environments than ECG and regular PPG sensors [20].Furthermore, the advances and challenges of wearable sweat analysis have been charted, with a focus on technical details and the capabilities of various biosensors [21].
In addition to the potential benefits of PHM, however, there are also inherent moral challenges.For example, what level of control and access should a soldier have over the information produced by their PHM device?What level of responsibility does a soldier bear for their evaluation of their own readiness based on insights from their PHM device?And how should conflicts between safeguarding a soldier's personal health through PHM and the interests of the military organisation be resolved, for example during a deployment?To illustrate this, consider the case of a soldier whose PHM-device indicates that he is exhausted and in need of rest, yet who is simultaneously under orders to maintain continuous observation of a military target.These questions highlight some values that may be at stake -often implicitly -when using PHM in the armed forces, such as autonomy, trust, and privacy [2,22].
There is a lack of research exploring the ethical dimension of PHM in military settings, despite existing research on this topic in civilian settings [23][24][25][26].Several subject matter experts from the member nations of the Multinational Medical Coordination Centre-Europe have recognised the need for further discussion of the ethical issues surrounding the use of biosensors in the military, such as in PHM [27].Research on the ethical dimension of PHM will extend the dialogue about the possibilities and success of PHM beyond the areas of acceptability, technical feasibility, and accuracy.It provides insight into the non-functional requirements necessary for successful PHM by exploring its values and moral considerations.Understanding the ethical dimension of PHM can promote awareness and facilitate morally responsible development, implementation, and usage of PHM in the armed forces.
This scoping review seeks to identify key concepts, knowledge gaps, and future research priorities regarding the inherent ethical dimension of PHM in the armed forces.In this study, we adopt the following working definition of the 'ethical dimension of PHM': the normative assumptions and descriptions, both implicit and explicit, of PHM.These assumptions and descriptions can be found within experiences, attitudes, (moral) questions, rules, and agreements.They inform us about what is considered right and wrong, desired and undesired, responsible and irresponsible.
In the military, the potential moral issues of PHM are compounded by the special nature of the organisation.According to the military oath, soldiers must adhere to military law and legislation, acquiring a different legal position than civilians.This requires them to follow orders and risk their lives in high-stake environments.Furthermore, soldiers are embedded in a military culture with its own moral standards, requiring them to work and be deployed in extreme and often hostile environments.These characteristics of the military context, together with the potential values at stake, call for an assessment of the ethical dimension of PHM within the specific military context.

Methods
A scoping literature review was completed to explore the available literature on the ethical dimension of PHM in armed forces.This review was conducted according to the JBI guidance for scoping reviews and is reported in accordance with the PRISMA extension for Scoping Reviews [28,29].To identify potentially relevant search terms, we used a broad naive search strategy in Pub-Med.Titles and abstracts of the references were screened to identify relevant search terms.Following this, the same set of references was utilized to apply keyword cooccurrence networks [30], facilitating the identification of additional relevant terms.Furthermore, text mining techniques were employed using VOS viewer [31] to construct and visualize co-occurrence networks of significant terms extracted from the initial search strategy.This comprehensive approach ensured thorough exploration and identification of relevant search terms for the study.
A comprehensive search of four bibliographic databases (Ovid/Medline, Embase.com,Clarivate Analytics/ Web of Science Core Collection, and Elsevier/SCOPUS) was conducted from the databases' inception to June 1, 2023 to identify relevant literature.Searches were devised in collaboration with a biomedical information specialist (KZ).The search terms "personal health monitoring" and "military", including synonyms, closely related words, and keywords, were used as index terms or free text words.The searches contained no methodological search filter or date or language restrictions that would limit results to specific study designs, dates, or languages.The references of included full-text studies were searched for additional relevant literature.
The full search strategy used for each database is detailed in appendix 1 Search strategy.

Study selection
Studies were included if they met the following criteria: (i) the study involved PHM according to the following definition: "any electronic device or system carried by an individual, that longitudinally monitors and records data about a health-related aspect of that individual's life"; (ii) the study had a focus on the ethical dimension of PHM according to our working definition; (iii) the study involved or addressed military personnel or claimed relevance of its contribution to the military.
Two pilot screenings in Rayyan -an application to facilitate the screening process [32] -were conducted to test the eligibility criteria and to reduce potential disagreement between the two reviewers.All titles and abstracts of the definitive search were screened by one reviewer (DB).Articles were labelled as: (1) include, (2) exclude, or (3) maybe.A second reviewer (EvB) independently screened a 10% random subsample.An active learning algorithm -ASReview (version 1.2.1) with default settings -was used for a second screening to determine if the experience of the first screening round resulted in a different outcome in terms of the included articles.Screening with ASReview was stopped after one hundred consecutive irrelevant records were screened [33].
Following the discussion of the title and abstract screening outcome between the two initial reviewers, the articles that were still labelled as 'maybe' were screened by a third reviewer (BM).Full-text screening followed, in which two reviewers (DB, EvB) independently screened each article.Discrepancies in judgement during both title and abstract screening and full-text screening were resolved through a consensus procedure [34].This involved a collaborative discussion among the reviewers to reach a mutual understanding about the screening outcomes until a consensus was achieved on the inclusion or exclusion of articles.

Data extraction and analysis
An extraction tool was developed in Microsoft Excel and used to extract data from the included studies.One reviewer (DB) extracted data from all included articles.The second reviewer (EvB) checked the extracted data for completeness.Data extracted were: (1) study characteristics, (2) methodology, (3) context, and (4) addressed ethical dimension, including illustrating examples from the articles.All sections of the articles were examined for relevant data.The data was analysed through Braun and Clark's qualitative thematic approach [35].The initial coding was conducted by one reviewer (DB).All three reviewers (DB, EvB, and BM) coded three articles.Following a collaborative discussion and consensus on the initial analysis, a second-order analysis was conducted to reflect on the emerging data and themes.This process led to the identification of categories that reflect the ethical dimension of PHM in the included studies.To support the analysis, the qualitative software program NVivo 12 was used to record codes and themes within the included articles.Insights, discussions, reflections, and decisions were recorded in separate notes.

Results
The literature search generated a total of 15,834 references: 2,050 in Ovid/Medline, 2,041 (excluding 1146 conference abstracts) in Embase.com,3,446 in Clarivate Analytics/Web of Science Core Collection, and 8,297 in Elsevier/SCOPUS.After removing duplicates of references that emerged from more than one database, 9,071 references remained.The flow chart of the search and selection process is presented in Fig. 1.
Following title and abstract screening, 39 articles were identified as potentially relevant for this study and were further assessed for eligibility.After full-text screening, 20 articles were excluded because they did not specifically report on PHM or did not sufficiently address the ethical dimension.This led to a final selection of 19 relevant articles for this review.Citation tracking did not yield any additional articles.
A comprehensive overview of the data extracted from the selected articles is provided in Table 1 Data extraction.Eleven articles originate from the United States, two from the United Kingdom and one each from Egypt, Finland, Germany, India, Iran, and The Netherlands.There are eight primary research studies, seven reviews, and four personal views.All articles have a qualitative nature.
The qualitative thematic analysis led to the identification of three categories reflecting the ethical dimension of PHM: 1) utilitarian considerations; 2) value-based considerations, and 3) regulatory responsibilities.

Utilitarian considerations
This category is characterised by descriptions of the reasons, causes, and consequences of the use of PHM.Thirteen articles address one or more of these utilitarian considerations, including proposed health benefits such as promotion of health, injury reduction, and increased self-awareness for users of PHM [2,22,[37][38][39][40][41][42][43][44].For • Data ownership (2) • Protection of user (3) • Regulation (3) • Liability (3) • However, these same biometric data come with the risk of compromising players' privacy and autonomy, as well as the confidentiality of their data.Moreover, they also have the potential to disadvantage players in contract negotiations and to harm, and even cut short, athletic careers example, according to Casselman, Onopa and Khansa wearables could be used to track vitals, reduce injuries, and help manage stress in the training of military and law enforcement personnel [39].In addition, Murdock and Hagen state that "Military operators perform at an elite level, and can benefit from technologies that can allow them to perform at an even higher level from personalized training, tracking and recovery" ( [42], p. 3).Another motivation for using PHM is to improve the access of soldiers to care by overcoming resource limitations and to enhance the quality of care by improving treatment compliance and enriching the available health information [42,[45][46][47].This is exemplified by Leightley and Murphy: "Emerging digital health technologies for mental health, such as the use of smartphone apps, web-based platforms and new data-driven analytics, could provide a means to overcome resource limitations and staffing, and reach individuals who are unable or reluctant to access mental healthcare" ([47], p. 2).The use of PHM could also provide organisational benefits, such as improving operational readiness, optimizing performance, and enhancing safety, as well as some financial advantages, including the reduction of healthcare costs [37,38,42,48].This is illustrated by Winslow and Mills, who claim: "Wearable technology is central to the future of service member modernisation, in which realtime physiological data will be persistently monitored to evaluate individual physical and mental health, maintain safety and optimise performance" ( [38], p. 2).Mohammadian et al. point out: "These technologies can help reduce hospital and nursing costs and provide care for the needy" ( [48], p. 448).Ng et al. mention, furthermore, that "Several participants stated that they hoped their Fitbit data would benefit future veterans, move research forward in the treatment of PTSD [Post-traumatic stress disorder], and support the development of the intensive outpatient programs" ( [41], p. 7).This indicates that there are also social contributions of PHM, such as opportunities for users to contribute to the military community and increased interactions between military members.Finally, PHM could be a means to support the well-being and health of society [48].
Most of the studies included in this review contain (implicit or explicit) utilitarian arguments, highlighting the benefits of PHM for users, as well as benefits at the organisational level in terms of operational readiness and performance.

Value-based considerations
Several studies explicitly mention the values at stake in the development, implementation, or actual use of PHM, as well as the concerns or dilemmas based on these values.Four main values are identified: (1) privacy, (2) security, (3) trust, and (4) autonomy.Additionally, conflict of interest representing moral dilemmas are presented.Three articles explicitly mention ethical issues related to PHM, but they do not provide a clear discussion of what these issues might be [41,45,48].

Privacy
Privacy in PHM is discussed in fifteen articles, primarily as a concern and occasionally as a consideration.It covers issues of individual and group privacy, storage of and access to data, implications for personal security, and proposed solutions such as privacy by design, which integrates privacy as a fundamental aspect in system development [37,40,41,46,[49][50][51][52][53].For example, in their discussion about individual privacy, Kröger, Lutz and Müller mention that "a more ubiquitous use of eye tracking will also raise serious privacy concerns -not only because gaze data may be collected and shared in non-transparent ways, but also because such data can unexpectedly contain a wealth of sensitive information about a user" ([52], p. 227).Austin states: "The unauthorized access of the user's data through theft, hack, or leak presents privacy risks to both the user and the organization" ([37], p. 6).In addition, Davison et al. state that "Privacy by Design is crucial in decreasing privacy risk and increasing trust" ( [49], p. 61).The authors also raise concern about the potential erosion of the perception of privacy in smart, sensorized environments.In the context of employee-employer relationship in professional sports, Karkazis and Fishman argue that "Because teams have a strong interest in gaining comprehensive information about players' health and performance, sport already pushes the limits of the employee-employer relationship with regard to privacy and surveillance", indicating a further degradation of individual privacy ( [40], p. 50).
Privacy concerns extend beyond the individual and can also affect group privacy.This is considered a flaw in current approaches to privacy protection, as noted by Metzger et al. [53].They illustrate this through a case in which aggregated anonymized individual data led to the unintended and unwanted identification of military groups.The authors state that "by threatening group privacy (e.g., revealing the location of a secret military base), the privacy and safety of individual group members (e.g., soldiers stationed on that base) are also threatened, even when the data are not linked to any of those individuals' identities" ( [53], p. 2).Additionally, in light of algorithms that group individuals based on certain characteristics, and offer predictive analytics, questions arise "about the collective's right not to be discovered in the first place because the action of clustering imposes an unwanted or unwarranted identity on people" ( [53], p. 60).

Security
Security concerns are expressed in eleven articles.Elhoseny et al. mention that "the security and privacy of data obtained from Medical Internet of Things devices…are becoming a major unresolved concern in healthcare, where less attention is paid by the industry and the academic community" ([50], p. 3).This concern is significant for networked technology due to the potentially disastrous consequences of a security breach on patient safety [39].Such a breach poses a risk not only to the individual but also to the organisation [22,37].Some authors suggest that a number of requirements, most of which are technical in nature, such as data integrity, data confidentiality, and authentication, should be met to ensure adequate security [46,50].Therefore, "security must be intrinsic to the design of wearable healthcare devices", according to Casselman et al. ([39], p. 1018).Elhoseny et al. similarly state that "the successful development and deployment of Medical Internet of Things must take security and privacy both as core considerations" ([50], p. 9).

Trust
Trust is also considered a crucial value.It is mentioned in seven articles, but only two of them provide a deeper analysis of its value and its relevance to PHM.Firstly, it is important that users trust the technology itself [47][48][49][50].For example, Leightley and Murphy argue: "As we move towards a more digitally connected world, it is important that we seek to build trust in the technology" ( [47], p. 2).Furthermore, there should be a relation of trust between the users of technology and its "prescribers", such as physicians or organisations [22,40,41].Karkazis and Fishman, for example, argue that "When team coaches and trainers are asked to make crucial decisions based on an athlete's biometric data, it threatens to compromise the trust-based relationships with players that are integral for a player's, and team's, success"( [40], p. 54).A similar trust-based relationship is also deemed crucial in the military.Illustrated by the absence of major privacy concerns amongst military users of PHM, their high level of trust in the military organisation highlights a potential vulnerability for them in terms of their ability to balance their risks and benefits [22].

Autonomy
Twelve articles discuss issues related to autonomy, which is connected to other values such as informed consent, transparency, confidentiality, and voluntariness.For example, Winslow and Mills recommend: "All applications should be private and transparent, and support individual consent, accountability and fairness" ( [38], p. 2).In addition, Stacey and Woods illustrate by mentioning "the freedom to achieve peak physical performance, which may on occasion fall a hair's breadth from physiological failure", that the collection of data from healthy military personnel can challenge personal autonomy ( [2], p. 291).Karkazis and Fishman argue that "the collection and storage of biometric data by employers and third parties raises risks of exploitation, coercion, and employee discrimination when these data are used in hiring and firing decision making", indicating a potential degradation of individual autonomy ( [40], p. 46).According to some authors, it is uncertain whether users of PHM have full autonomy in their relationship with the organisation or team to which they belong, which could affect their ability to make independent decisions about using PHM [22,40].

Conflict of interest
Two articles mention potential conflicts between individual and organisational interests.Karkazis and Fishman argue that the use of biometric data can lead to a conflict of interest between professional athletes and the organisations that employ them.The authors illustrate this by saying that "these [biometric] data inform decisions that are beneficial to both a player and a team's long-term goals…however, at times, trainers and coaches may use data to make decisions that ultimately run counter to a player's wishes, and perhaps involve disclosing private player information to team management" ( [40], p. 51).In addition, they discuss the role of team physicians, who are obligated to provide care to the individual athlete and at the same time act in the team's best interest.This dual loyalty of the team physicians presents another potential conflict of interest when the athlete's and team's interest do not align.Furthermore, it is argued that a soldier's individual interests in relation to PHM, such as privacy, need to be considered alongside organisational interests, such as security, as there is a potential for these to collide.Consequently, a conflict of interest may arise [22].These conflicts reflect potential moral dilemmas between values such as autonomy, privacy, security and trust.

Regulatory responsibilities
Various articles report a clear need for increased regulation, particularly regarding data security and privacy, with responsibilities shared between the government and the industry [39,46,50,52].Kröger, Lutz and Müller consider it "to be primarily the responsibility of technical experts, technology compagnies, and governmental agencies to inform consumers about potential consequences and protect them against such covert invasions of privacy" ( [52], p. 236).This is also recognised by Casselman, Onopa and Khansa, who claim an important role for industry and government to "help ensure control measures are built in and enforced" to address challenges regarding data security and privacy ( [39], p. 1019).PHM design and development should be subject to rigorous standards; verification, validation and certification methods should be standardised, with cybersecurity being a key focus [38,47].In addition, it is believed that without adequate regulation, technological advancements such as PHM may not receive sufficient funding and adoption, thus failing to reach their full potential [39,50].It is also deemed important to consider liability issues under health and safety legislation, for example when an employer receives data that indicates that an employee's health status is affecting their ability to work [40].

Discussion
This scoping review identified three dominant themes in the existing literature on the ethical dimension of PHM in the military: utilitarian considerations, value-based considerations, and regulatory responsibilities.Many authors consider the use of PHM to be beneficial, citing potential improvements in health, care, and organisational outcomes.While most authors implicitly refer to values as the foundation for the design, implementation, and use of PHM, few address any specific threats to these values, or more specifically value conflicts that may arise.At the same time, several authors call for increased regulation and control measures, particularly in order to safeguard privacy and security issues.It is important to note that there is a significant lack of empirical research focussing specifically on the ethical dimension of PHM in the military.
The articles included in this review primarily focus on utilitarian arguments that emphasise the potential benefits of using PHM, without explicitly weighing them against potential disadvantages.This may produce an implicit bias towards the benefits of PHM.This bias may reinforce the belief that biometric technologies are more precise and objective than other measures, and that their data is easier to interpret and act upon [40].However, it has been demonstrated that the validity and interpretation of data and the underlying algorithms from wearable sensors is not as precise as often assumed, particularly when used outside laboratory settings [54].Furthermore, it is generally acknowledged that, while data may appear objective, the algorithms that process these data may be biased, for example through a lack of diversity in validation studies [55][56][57].There also seems to be a strong belief that "to measure is to know" and that what is known can be improved [58].This can leave little room for discussion on whether this desire for improvement, by using PHM, is justified.
Numerous studies demonstrate benefits of PHM, for example in health promotion and prevention of health problems [59], treatment [60] and rehabilitation [61].The use of PHM in the articles in this review is often justified, prioritising the desired outcome, such as improved health.This outcome appears to justify the means, although this argument often remains implicit.However, such a perspective, even unintended, does not provide a critical assessment of the potential downsides of PHM, such as its impact on the wearer, adverse effects, and data management and privacy issues.Critical appraisal involves balancing the desired outcomes of PHM against its potential side effects or risks.This is necessary to make a responsible decision about the use of PHM.
The use of PHM involves several interrelated values that may be at stake, as identified in this scoping review.These include informed consent, transparency, voluntariness, trust, and autonomy.This interrelatedness requires a more thorough analysis of the impact of these values on each other and on the intended purpose of PHM.Additionally, some of these values may conflict with assumed benefits: the level of privacy may decrease in order to optimise performance within the military, or relations of trust between military users of PHM and their leadership may deteriorate when personal and organisational goals diverge.
Many authors mention privacy concerns related to the use of PHM, but they often focus only on individual privacy.While these are valid concerns, in the age of data technologies, privacy concerns extend beyond the individual and should also be considered from a group perspective [62].It is important to note that the law protects individuals against discrimination based on shared characteristics like race, religion, or gender.However, this protection does not yet extend to algorithmically grouped individuals, for example those who are monitored by a PHM device and grouped based on their behaviour.This may involve identifying previously unknown or anonymous (sub)groups and making interventions based on that information [53].Even when anonymised, PHM data could lead to the identification of groups of military personnel with, for example, a higher likelihood of service disability, which could in turn have legal consequences.This raises questions regarding the permissibility of such identification, the potential legal consequences, how the military organisation handles this, and whether military personnel who are identified as belonging to a risk group can defend themselves against the consequences of such identification.Therefore, the interest of group privacy formed by algorithmic classification should be balanced against other moral considerations and concerns, such as individual privacy [63].Additionally, this kind of identification raises concerns about the potential impact on the support for and trustworthiness of PHM if users become aware of such identification and the consequences.The authors of the current review therefore recommend that employers and regulators more carefully consider the extent to which employers should want and should be permitted to access information that may harm group privacy interests.
In the majority of the included articles, the moral considerations and values at stake in PHM are presented in a rather binary manner, such as the need for PHM to be secure.This perspective oversimplifies the multifaceted nature of security, which is intertwined with other values, including privacy, trust, and confidentiality.It is important to consider the specific situation, circumstances, and purpose of PHM, as this context influences the degree of interconnectivity between different values and their share in PHM.For example, in the context of civilian healthcare, PHM must adhere to higher standards of privacy and security than consumer-based (lifestyle) PHM devices [64].In the US, regulatory clearance or approval by the Food and Drug Administration (FDA) is required for PHM to be authorized for use in healthcare.In the EU, a CE certificate is necessary.In comparison, in the military, PHM data could be considered strategic and therefore valuable to adversaries.The implication of this is that the use of PHM in the military should adhere to the same or even higher security standards than in civilian healthcare.
When discussing PHM in the military, we recommend considering the interconnectivity of various values, such as the balance between privacy and security and how this plays out in a specific context.We also recommend including the perspectives of various stakeholders.This approach can help align individual and organisational interests, identify potential areas of conflict, and make well-considered trade-offs between the values involved.Merely arguing for maximum privacy and security without considering their costs, considering specific situations, or being responsive to needs of different stakeholders will not deepen our understanding of the ethical dimension of PHM in the armed forces.The aim of this scoping review is not to provide decisive and normative evaluations of what is right and wrong in PHM.Rather, it is to encourage an open dialogue among relevant stakeholders, so they can engage in a critical and informed discussion about the potential benefits of PHM and how its (dis)advantages and inherent moral considerations may be balanced.This should be done by taking into account the differences in perspectives and the specific contexts in which PHM in the armed forces will be developed or deployed.For example, the implementation of PHM in the military requires a different discussion when promoting individual health and readiness than when the goal is to increase mission success, potentially at the expense of the wearer.An open dialogue approach would benefit the transparent development, implementation, and use of PHM.This transparency has the potential to strengthen trust relations between users, developers, physicians, and commanders.In particular, within the context of the military, where there is a strong hierarchy and limited autonomy for military PHM users, the organisation has an even greater responsibility to take the ethical dimension of PHM into account.
By analogy with privacy by design, which integrates privacy considerations into the development process rather than treating them as an afterthought, the key may be to incorporate ethics into the design, implementation, and application of PHM, while considering the specific nature of the military environment.This incorporation of ethics by design can be found in value-sensitive design, that is, "a theoretically grounded approach to the design of technology that accounts for human values in a principled and comprehensive manner throughout the design process" ([65], p. 2).While this approach, like others, has its limitations [66], it is a design framework useful for bringing together conceptual, empirical, and technical investigations of relevant values [67].This will enrich the discussion about the design of PHM beyond functional or legal aspects [68].
This scoping review shows that there is currently a lack of academic literature that specifically explores the ethical dimension of PHM in the armed forces.Understanding this dimension is key to achieving the morally responsible development, implementation, and use of PHM within the military.We encourage empirical research on the ethical dimension of PHM in the military.This can aid in understanding the ethical dimension of PHM by reflecting on specific examples of PHM and the perspectives of various stakeholders.Such studies should consider both the benefits of PHM on an individual and organisational level, as well as potentially conflicting values, and how to balance them.

Strengths and limitations
To our knowledge, this is the first review to identify the ethical dimension of PHM in the military, shedding light on key principles and values.The ethical dimension was identified through an extensive search of academic literature and a comprehensive review of the included articles.This study highlights a significant research gap on the ethics of PHM in the military.The insights gained from this study can stimulate future empirical research.Furthermore, the aim of this review is to raise awareness among developers and policymakers in the military domain regarding the integration of ethical deliberation on PHM, for example through value-sensitive design, in order to achieve a morally responsible development, implementation, and use of PHM.
There are also some limitations to consider.The eligibility criteria were broad and there were few search restrictions, resulting in an initial screening of over 9000 articles.Manual screening of such large amounts of data carries the risk of human error in terms of inclusion or exclusion due to the monotonous nature of the task.However, this risk was mitigated by dividing the screening process into smaller sections.Furthermore, identifying ethical concepts in articles that do not explicitly address them is quite difficult, and this is a significant limitation of this scoping review.Our working definition of 'ethical dimension' includes implicit normative assumptions and descriptions of PHM.However, it was challenging for the reviewers to identify and describe these implicit assumptions and descriptions from all the different sections of the articles, while minimizing subjectivity.
Furthermore, some articles discussing relevant technologies related to PHM, such as Wireless Body Area Networks (WBAN), Internet of Things (IoT), and Internet of Medical Things (IoMT), were included instead of solely focusing on PHM.Potentially relevant articles may have been missed because these technologies were not systematically considered during the screening process.In addition, only a 10% subsample of the 9000 identified articles were screened by a second reviewer.Although the two reviewers agreed to a high degree about the relevant articles in the subsample, there is still a possibility that relevant articles were missed.As reviewers gain experience during the review process, it is likely that their assessments of articles will develop, leading to differences between the first articles screened and the last ones.During the early stages of screening, articles may have been excluded, potentially leading to a less comprehensive final selection.While an active learning algorithm was used to verify a portion of the included studies, it is important to consider this limitation.
Lastly, although the authors suggest that the ethical dimension of PHM in the military requires a separate assessment due to the unique nature of the military environment, it is unclear if this perspective is widely shared among scholars.This may account for the limited availability of academic literature on this topic.moral competence by means of ethics education and on developing interventions that contribute to a 'just culture' and psychological safety in organisations.EvB also works as a research associate at the Department of Ethics, Law & Humanities, Amsterdam University Medical Centres, location VU University Medical Center, Amsterdam, The Netherlands.KZ worked as a biomedical information specialist at the medical library at the VU University Amsterdam and the Amsterdam University Medical Centres, location VU University Medical Center, Amsterdam, The Netherlands.The focus of her research was on automatization and AI in literature research.Currently, KZ works as a data scientist with a focus on healthcare capacity management in Dijklander Ziekenhuis, a regional hospital in Hoorn/Purmerend, The Netherlands.BM is full professor of Clinical Ethics Support and Quality of Care both at a) the Department of Ethics, Law & Humanities (ERH) at Amsterdam University Medical Centres and the VU University, and also works at b) the Centre of Medical Ethics, University of Oslo, Norway.In Amsterdam, he is head of the section Ethics Support & Research Integrity and member of the ERH management team.His main tasks are research, supervising PhD research, training and consultancy related to ethics support (e.g.moral case deliberation) and empirical ethics.He is co-founder and former coordinator of both the European Clinical Ethics Network (ECEN; since 2005) and the Dutch Network for Ethics Support (NEON; since 2014).He is also General Secretary in the executive board of the European Association of Centres for Medical Ethics.

Funding
No funding was received for conducting this study.

Fig. 1
Fig.1Flow chart of the search and selection process[36]